login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A237929 Numbers n such that (i) the sum of prime divisors of n (with repetition) is one less than the sum of prime divisors (with repetition) of n+1, and (ii) n and n+1 have the same number of prime divisors (with repetition). 2
2, 9, 98, 170, 1274, 4233, 4345, 7105, 7625, 14905, 21385, 30457, 34945, 66585, 69874, 77314, 82946, 98841, 175354, 177122, 233090, 236282, 238017, 263145, 265225, 295274, 298082, 322234, 335793, 336106 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The first term a(1)=2 is the only prime number in this sequence.

LINKS

Abhiram R Devesh, Table of n, a(n) for n = 1..96049

EXAMPLE

For n=98: prime factors = 2,7,7; sum of prime factors = 16; number of prime divisors = 3

For n+1=99: prime factors = 3,3,11; sum of prime factors = 17; number of prime divisors=3.

PROG

(Python)

## sumdivisors(n) is a function that would return the sum of prime

## divisors of n

## numdivisors(n) is a function that would return the number of prime

## divisors of n

i=2

while i < 100000:

..sdi=sumdivisors(i)

..sdip=sumdivisors(i+1)

..ndi=numdivisors(i)

..ndip=numdivisors(i+1)

..if sdi==sdip-1 and ndi==ndip:

....print i, i+1

..i=i+1

CROSSREFS

Cf. A001414, A006145 Ruth-Aaron numbers (1): sum of prime divisors of n = sum of prime divisors of n+1.

Cf. A228126 Sum of prime divisors of n (with repetition) is one less than the sum of prime divisors (with repetition) of n+1.

Cf. A045920 Numbers n such that factorizations of n and n+1 have same number of primes (including multiplicities).

Sequence in context: A013132 A317275 A013057 * A227258 A027686 A187647

Adjacent sequences:  A237926 A237927 A237928 * A237930 A237931 A237932

KEYWORD

nonn

AUTHOR

Abhiram R Devesh, Feb 16 2014

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 27 23:16 EDT 2021. Contains 346316 sequences. (Running on oeis4.)